Methods and devices for personal water craft

ABSTRACT

Jet-powered water craft have become popular recreational pleasure craft for people worldwide as well as providing rapid response in a water environment for life savers, police, customs, etc. However, once the throttle has been cut there is no braking or steering mechanism for such craft. Equally such braking or steering is limited at low speeds. Accordingly it would be beneficial to provide means for braking and/or steering such jet-powered water craft under low speed operation and/or when the throttle is cut. According to embodiments of the invention such mechanisms are provided whilst providing for ease of use during operation as well as beaching/launching/storage.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application claims the benefit of U.S. Provisional PatentApplication 61/471,764 filed Apr. 5, 2011 entitled “Methods and Devicesfor Personal Water Craft.”

FIELD OF THE INVENTION

This invention relates to personal water craft and more specifically tomechanisms for braking them and steering them at low speed.

BACKGROUND OF THE INVENTION

Jet-propelled water craft have become popular recreational/pleasurecraft for a significant number of people across a wide age range throughfactors such as ease of use, stability, and safety from lack of bladetype propulsion. This ease of use also stems from the fact that they aretypically designed to be steered using exhaust fluid flow pressuredeveloped from a movable jet nozzle submerged below the surface of thewater. However, as the throttle-controlled thrust is retarded, theability of the user to steer the water craft is substantially reduced oreliminated. Further, as most jet-propelled water craft have no rudders,any type of substantial reduction in exhaust pressure, coupled with asteering capability that depends upon a steerable exhaust nozzle,typically makes it impossible to steer such water craft effectively atanything than other than when the exhaust pressure is high.

However, when the user reduces the throttle or cuts the throttle,thereby reducing or cutting the exhaust pressure respectively, and isriding without any steering, the water craft is prone to cause accidentssince the momentum of the water craft and its inertia caused by thethrust produced by the jet stream of water just prior to being cut willpropel the craft in that given direction.

Within the prior art various mechanisms have been proposed to providealternative steering capability for jet-propelled water craft. However,such mechanisms have shortcomings. For example, some rudder mechanismsrequire manual operation to deploy into the water, or to be removed fromthe water. Spring-biased rudder mechanisms, while providing the abilityto displace upwardly upon contact with foreign objects, typically remainin the water at all times, producing excessive drag during high-speedoperation of the water craft. As an example see FIGS. 4 and 5 thatdepicts the teachings of Adomeit in U.S. Pat. No. 6,878,020 entitled“Jet Boat Emergency Braking System” and Murray in U.S. Pat. No.6,086,437 entitled “Blow Back Rudder for a Water Craft” respectively.Finally, some of these mechanisms are designed to deploy automatically,see for example Posti in U.S. Pat. No. 3,982,494 entitled “AuxiliaryRudder for a Jet Propulsion Unit”, and depicted in FIG. 1, wherein apiston controlled by water pressure to raise the rudder as speedincreases is presented. However, at low speed and cut-throttle suchrudders trail behind the behind the water craft with significantelements above the water line Thus, such devices present a significantsafety hazard to anyone falling off of the water craft during use.

Other attempts to deal with the problem of providing slow speed steeringcontrol to jet-powered water craft in a safe and efficient mannerinclude the use of a third class lever connected to a rudder, whichpivots from the uppermost portion of the lever, where it is attached tothe jet nozzle. Thus, the rudder extends behind the craft for somedistance while deployed in the steering position, and extends bothbehind the craft and above the water line while in the stowed or“running” mode. Such operational characteristics present a significanthazard to any operator, or passenger of the water craft that falls tothe rear of the craft during operation. Further, re-boarding of thecraft after a fall is quite difficult if the rudder apparatus projectsinto the path of the boarding operator and/or passenger.

In an alternate approach Pereira in U.S. Pat. No. 5,970,898 entitled“Jet Ski” teaches to a foot activated braking paddle for a jet-propelledwater craft. Unlike other approaches the braking paddle is deployed fromthe middle portion of the hull as evident in FIG. 2. Other examples ofsuch approaches include Adomeit in U.S. Pat. No. 6,652,333 entitled “JetBoat Steering System”, and Swartz in U.S. Pat. No. 6,443,785 entitled“Method and Apparatus for Self-Deployed Rudder Assembly.” Willis in U.S.Pat. No. 7,168,384 entitled “Personal Water Craft Braking Apparatus”provides a variant to the deployment of brakes into the exhaust nozzleflow to dig the stern of the water craft deeper into the water ratherthan simply re-directing the exhaust flow in other than the direction ofmotion of the water craft, as depicted in FIG. 3.

Generally the prior art approaches do not allow for adjustments in thelevel of thrust required to deploy and/or store the rudder based on theexhaust pressure developed at idle or low speeds being primarily focusedto higher exhaust pressures, nor do such devices allow for raising therudder completely out of the way for beaching/launching/storing thejet-powered water craft. Similarly the provision of operator activatedbrakes does not allow for the scenarios where the rider has been thrownoff and the water craft is progressing forward under its own momentum.

Accordingly, it would be evident to one skilled in the field that thereexists a requirement to be able to steer/brake a jet propelled watercraft under circumstances that include but are not limited to when thethrottle is cut and no thrust is being produced by the jet nozzle andwhen the throttle is operating and low thrust is being produced by thejet nozzle. It would be further beneficial for such mechanisms ofsteering/braking to be compatible with the beaching/launching/storing ofthe jet powered water craft as well as the users' ability tomount/dismount/use the jet-powered water craft.

SUMMARY OF THE INVENTION

It is an object of the present invention to address deficiencies in theprior art with respect to personal water craft and mechanisms forbraking them and steering them at low speed.

In accordance with an embodiment of the invention there is provided adevice comprising a hull forming a predetermined portion of a watercraft and a first channel comprising a predetermined portion of the hullhaving disposed within at least one flap of a plurality of flaps, eachflap comprising at least a first surface and being positionable betweena first position and a second position wherein the flaps positionbetween the first and second positions is determined in dependence uponthe pressure applied by water impinging upon the first surface resultingfrom motion of the hull through the water.

In accordance with an embodiment of the invention there is provided adevice comprising:

-   a hull forming a predetermined portion of a water craft;-   a nozzle mounted in a predetermined location on the hull receiving    water via a channel forming a predetermined portion of the hull and    exhausting said water to provide variable thrust for the water craft    between zero and a maximum thrust;-   a first flap comprising at least a plate and a mounting, the    mounting for attaching the plate to the hull in a predetermined    location and allowing the plate to pivotably displace between a    first predetermined position and a second position wherein the plate    is disposed at the first predetermined position when the thrust is    zero, at a third position intermediate the first predetermined    position and the second position when the thrust is the maximum    thrust, and additional positions between the third and second    positions in dependence upon the thrust of the nozzle and the    velocity of the water craft.

In accordance with an embodiment of the invention there is provided adevice comprising:

-   an engine comprising at least a drive shaft and operating in    dependence upon an engine control signal;-   a first coupling selectably engageable with a drive shaft of the    engine and comprising a first impeller shaft;-   a first exhaust providing thrust to a water craft through the    exhausting of water under pressure from the first exhaust, the    pressure generated by a first impeller coupled to the first impeller    shaft;-   a second coupling selectably engageable with another drive shaft and    comprising a second impeller shaft;-   a second exhaust providing thrust to a water craft through the    exhausting of water under pressure from the second exhaust, the    pressure generated by a second impeller coupled to the second    impeller shaft, wherein-   the first and second exhausts exhaust in opposite directions thereby    allowing one of the first and second exhausts to provide driving    thrust and the other of the first and second exhausts to provide    braking thrust.

Other aspects and features of the present invention will become apparentto those ordinarily skilled in the art upon review of the followingdescription of specific embodiments of the invention in conjunction withthe accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described, by way ofexample only, with reference to the attached Figures, wherein:

FIG. 1 depicts a prior art rudder according to Posti in U.S. Pat. No.3,982,494;

FIG. 2 depicts a prior art brake according to Pereira in U.S. Pat. No.5,970,898

FIG. 3 depicts a prior art brake according to Willis in U.S. Pat. No.7,168,384;

FIG. 4 depicts a prior art rudder according to Adomeit in U.S. Pat. No.6,878,020

FIG. 5 depicts a prior art rudder according to Murray in U.S. Pat. No.6,086,437

FIG. 6 depicts a braking method according to an embodiment of theinvention;

FIG. 7 depicts the braking method according to an embodiment of theinvention under different scenarios.

FIG. 8 depicts a brake deployment mechanism according to an embodimentof the invention;

FIGS. 9A and 9B depict a brake deployment mechanisms according to anembodiment of the invention;

FIGS. 10 and 11 depict rudder/brake elements according to embodiments ofthe invention;

FIGS. 12 and 13 depict a rudder/brake mechanism according to anembodiment of the invention; and

FIG. 14 depicts a rudder/brake mechanism according to an embodiment ofthe invention.

DETAILED DESCRIPTION

The present invention is directed to personal water craft and morespecifically to mechanisms for braking them and steering them at lowspeed.

Referring to FIG. 6 there is depicted a braking method according to anembodiment of the invention. As shown is a jet-powered water craft 600from a rear elevational perspective showing the central body 610, thesteering column 620, hull 630, and exhaust 680. Disposed into the hull630 near the exhaust 680 are first channels 660 that have within themfirst brake flaps 670. Disposed to the outer edges of the hull 630 aresecond channels 640 with deployed within them second brake flaps 650.The operation of these first and second brake flaps 670 and 650respectively is shown schematically in FIG. 7 by first and secondcross-sections 700A and 700B respectively that are taken along thesection X-X depicted in FIG. 6.

Referring to first cross-section 700A the jet-powered water craft isshown where the exhaust is non-operational or at low thrust (i.e. idlingor low throttle). Accordingly the plurality of second brake flaps 650within the second channel 640 are depicted as projecting forward suchthat any forward momentum results in the water being channeled into theregions between the second brake flaps 650 wherein it encounters thephysical wall structure of second channel 640 thereby providing abraking effect. As the exhaust is increased and forward momentumincreases the water pressure on the second brake flaps 650 increasesthereby causing them to pivot about their mounting such that at higherexhaust/velocity they are deployed as depicted in second cross-section700B. In this scenario the plurality of second brake flaps 650 are nowacting to channel water flow increasingly towards the rear of the watercraft thereby reducing the braking effect.

As would be evident to one skilled in the art this embodiment of theinvention provides for breaking that is automatic as the position of thesecond brake flaps 650, and correspondingly first brake flaps 670 whichare not shown for clarity, is dependent upon the velocity andcharacteristics of the brake flaps only. As such a reduction in forwardmomentum results in increased braking, leading to reduced velocity,increased braking etc. The brake flaps may be established in theirdefault breaking position by a combination of mechanisms including forexample springs, memory metals etc. In order to reduce fouling etc thespring mechanisms may be housed within the hull 630 of the jet-poweredwater craft. It would be evident that this approach allows easystorage/launching/beaching as nothing projects below the hull 630 or ifit does the brake flaps will automatically pivot with any physicalengagement to a beach/support etc. It would also be evident to oneskilled in the art that predetermined sub-sets of the plurality of brakeflaps within each channel may have different thresholds fortransitioning thereby providing a different braking profile or thatdifferent channels may have different thresholds.

Now referring to FIG. 8 there is depicted an alternate method ofdeploying a physical structure for a jet-powered water craft. As shown astructure 800 comprises a plate 810 that can move between a firstposition 820 to a second position 830. The plate 810 is mounted viafirst, second, and third arms 840A to 840C respectively to mount 880attached to the water craft body. The second and third arms 840B and840C respectively being attached to slider 890 that slides within agroove 850 of the mount 880 whilst first arm 840A is pivotably mountedto one end of the mount 880. A spring, not shown for clarity, or othermechanism provides tension to keep the plate 810 in first position 820when there is no pressure against the plate 810.

Increasing pressure against the plate 810 results in the first to thirdarms 840A to 840C respectively in combination with the fixed pivot andslider 850 providing a resultant motion 870 for the plate 810 betweenthe first position 820 and second position 830 according to the pressureapplied and the characteristics of the structure 800 including but notlimited to friction of slider 850 in mount 880 and the tensionalcharacteristics of spring. As such with increasing momentum and watervelocity the pressure on plate 810 increases thereby translating theplate 810 towards the second position 830 wherein it provides reducedrestriction to water flow and thereby reduced braking effect on thewater craft.

Referring to FIG. 9A there is depicted a first deployment scenario 900according to an embodiment of the invention wherein a first mechanism920 is disposed to one side of the exhaust flow from an exhaust 910 anda second mechanism 930 is disposed to the other side of the exhaustflow. Initially at rest the plates are disposed in their first positionand restrict the flow from the exhaust. Initially the increased exhaustflow pushes each of the plates within the first and second mechanisms toa position wherein they are outside the flow at some intermediateposition between the first and second positions. Now as velocityincreases for the jet-powered water craft water flow either side of theexhaust 910 increases thereby further increasing pressure on the platessuch that as the velocity of the water-craft increases they continue tomove to their second position with lowest resistance to water flow.Accordingly it would be evident that first deployment scenario providesfor highest braking when the exhaust is zero/low and then providesintermediate braking as the velocity increases with the exhaust at fullthrottle (or close to it) and then continues to reduce the appliedbraking force as velocity of the jet-powered water craft increases. Assuch the braking characteristic is ongoing even once full throttle hasbeen initially engaged as the craft begins to increase speed.

Now referring to FIG. 9B there is depicted a second deployment scenario900B according to an embodiment of the invention wherein a firstmechanism 940 is disposed to one side of a mounting plate 960 and asecond mechanism 950 is disposed to the other side of the mounting plate960 wherein these elements are laterally displaced from the exhaust flowprovided by exhaust 910. Accordingly in this scenario the position ofeach plate is now determined solely by the water flow arising from theforward momentum of the jet-powered water craft rather than having anydependence upon the exhaust flow from the exhaust 910. As suchincreasing velocity of the jet-powered water craft results in the platesmoving to their second position with reduced resistance. At low speedthe plates are thereby deployed providing braking resistance to thejet-powered water craft.

It would be evident to one skilled in the art that the combination offirst and second mechanisms 940 and 950 together with the mounting plate960 may be deployed in secondary channels within the hull of thejet-powered water craft rather than directly adjacent to the exhaust910. It would be further evident that providing a pair of these eitherside of the exhaust 910, wherein the mounting plates 960 are verticallydisposed rudder elements coupled to the steering of the jet-poweredwater craft, provides for a rudder assembly that provides increasedresistance/control at low velocity with reduced resistance control athigh velocity wherein primary direction may be still therefore derivedfrom the directional adjustment of the exhaust 910 for example.

It would be evident to one skilled in the art that the profile of theplate position (or angle relative to the water flow from the exhaustnozzle) with thrust may be varied according to a variety of factorsincluding but not limited to the design of the water craft, acharacteristic of a target user of the water craft such as novice,beginner, or expert, and legal requirements in the jurisdiction of useof the water craft. Optionally the braking structure such as provided bythe first and second mechanisms may be attached to the nozzle such thatthe braking is determined primarily from the nozzle irrespective ofdirection of the nozzle as in some water craft the nozzle may be pivotedto change direction.

Referring to FIG. 10 there is depicted an element 1000 according to anembodiment of the invention that may form part of the plates within thefirst and second mechanisms 910 and 920 of FIG. 9A or 940 and 950 ofFIG. 9B as well as the mounting plate 960 for example. As shown theelement 1000 comprises a vertical plate 1020 that terminates at eitherdistal end in distal plates 1010. Such a structure having been shown toprovide improved steering performance, as a rudder, at low velocityversus a rudder comprising only vertical plate 1020. It would be evidentthat the distal plates 1010 may require additional structure in the hullto accommodate them as they move.

Referring to FIG. 11 there is depicted an element 1100 according to anembodiment of the invention for providing a plate as part of a rudderand/or brake assembly that has a variable resistance with velocity ofthe water craft. As shown the element 1100 comprises a central member1110 with side panels 1120 disposed. Whilst central member 1110 may beformed from a rigid material the side panel 1120 is formed from aflexible material and is hollow being filled with a gas at apredetermined pressure. At low velocity the water pressure isinsufficient to distort the outer surface of the central member andtherefore the side panels 1120 provide a bulbous cross-section of theelement 1100. At increased speed the water pressure on the side panel1120 increases such that the gas within compresses and the profile ofthe panel 1120 reduces. If the side panels were used in combination withchambers within the central member 1110 then it is feasible to considerthat at increased pressure the side panels 1120 flatten substantiallyresulting a narrow less bulbous profile for the element 1100. As suchthe efficiency of element 1100 as a rudder is directly related to thevelocity of the jet-powered water craft such that its efficiency ishighest at low velocities.

It would be evident to one skilled in the art that said chambers may befitted with pressure valves such that gas flow between the side panelsand chambers occurred as predetermined pressure thresholds were met.

Now referring to FIG. 12 there is depicted brake/rudder assemblyaccording to an embodiment of the invention at rest in firstcross-section 1200A and at speed in second cross-section 1200B. In firstcross-section 1200A at rest (or low velocity) the brake/rudder assembly1210 is deployed in a down ward direction providing the requiredsteering capability as well as braking, as will be evident in referenceto FIG. 13 wherein the concept is presented from a front-elevationperspective. As the velocity increases and pressure on the rubber/brakeassembly 1210 increases it is deflected back and up into the hull of thejet-powered water craft and as evident in FIG. 13 forms a closed coverto the recess 1220 in the hull.

Accordingly referring to FIG. 13 first view 1300A corresponds todeployment of the rudder/brake assembly 1210 at zero or low velocity andsecond view 1300B corresponds to deployment at higher velocity asdescribed in relation to second cross-section 1200B. Referring to firstview 1300A there is shown the recess 1220 and brake/rudder assembly 1210which comprises central member 1310, first side member 1320 and secondside member 1330. As evident in FIG. 12 this deployment results in thebrake/rudder assembly 1210 being substantially disposed as aconventional rudder below the jet-powered water craft but at the bowrather than the stern. Whilst steering from bow mounted rudders hasreduced efficiency this is still a significant improvement compared tothe absence of control/rudder from existing commercial jet-powered watercraft when the exhaust is cut or reduced.

Now referring to second view 1300B at increased velocity the waterpressure has pushed the brake/rudder assembly 1210 back which due to thepivot 1350 also results in it coming up against the hull and into therecess 1220 within the hull. Simultaneously the pressure on the firstand second side members 1320 and 1330 respectively has resulted in thembeing pushed about their pivot mountings, not shown for clarity, suchthat they open, essentially like the front and back covers of a bookwith the central member 1310 as the spine of the book. In this mannerthey are pushed back, up, and out so that the overall result is theyform a cover to the recess 1220 at increased velocity. It would beevident to one skilled in the art that the brake/rudder assembly 1210may also be augmented with a manual mechanism to raise the brake/rudderassembly into position or lock it allowing eased storage/launching.

Within the embodiments of the invention described with respect to FIGS.6 to 13 the control of the rudder/brake deployment has been driventhrough exploiting automatic physical aspects of the combination ofweight, torsion, pressure etc in varying combinations. However, it wouldbe evident to one skilled in the art that these mechanisms may beaugmented with a system exploiting the engine of the jet-powered watercraft or replaced in other scenarios.

Referring to FIG. 14 there are depicted first and second jet controlscenarios 1400A and 1400B respectively. Considering first jet controlscenario 1400A then there is depicted the conventional combination ofengine 1410, exhaust 1420 and first coupling 1430 from the engine driveshaft to the shaft of the exhaust 1420 which is usually a waterproofcoupling sealed at the wall of the hull as the drive must transitionthrough from the inner air filled hull region to the water filledchannel within which the exhaust 1420 operates. In this example firstcoupling 1430 is modified to couple/decouple the exhaust drive shaftfrom the engine drive shaft. Additionally a second coupling 1440 isshown that would be coupled to second exhaust 1450.

Considering initially the case of normal throttle operation as thejet-powered water craft is intended to move forward for the user thenthe exhaust 1420 is coupled to the engine 1410 and exhaust flow providesforward momentum. However, if the user now reduces or kills the throttlethen the first coupling 1410 is decoupled and second coupling 1440engaged such that the second exhaust 1450 operates thereby providingreverse thrust to act as a brake for the water craft.

Now referring to second jet control scenario 1400B the second exhaust1450 has been replaced by first and second thrusters 1470 and 1480 whichare coupled to the second coupler 1440 via third coupler 1460. Accordingfirst and second thrusters 1470 and 1480 can provide braking thrust tothe jet-powered water craft. However, it would also be evident that theproportion of thrust applied by each of the first and second thrusters1470 and 1480 may be varied through operation of the third coupler 1460and that this adjustment may be established in response to the usersactions with the steering of the jet-powered water craft.

It would be apparent to one skilled in the art that first and secondthrusters 1470 and 1480 may be directed to single exhausts each ormultiple exhaust ports. It would also be apparent that the embodimentsof the invention described with respect to FIGS. 6 through 14 may beused individually or in combination to provide different controlconfigurations as well as different combinations of braking/steering.

The above-described embodiments of the present invention are intended tobe examples only. Alterations, modifications and variations may beeffected to the particular embodiments by those of skill in the artwithout departing from the scope of the invention, which is definedsolely by the claims appended hereto.

1. A structure comprising: a hull forming a predetermined portion of awater craft; a first channel disposed within the hull; and at least oneflap of a first plurality of flaps disposed within the first channel,each flap comprising at least a first surface and being positionablebetween a first position and a second position wherein the flapsposition between the first and second positions is determined independence upon the pressure applied by water impinging upon the firstsurface resulting from motion of the hull through the water.
 2. Thestructure according to claim 1 wherein, the first channel is disposed inthe bow of the water craft; and the at least one flap is disposed so asto cover the channel in the first position and expose the channel in thesecond position.
 3. The structure according to claim 1 wherein, theplurality of flaps automatically return to the first position when thepressure applied to the first surface is below a predetermined value. 4.The structure according to claim 1 further comprising; a second channeldisposed within the hull; and at least one flap of a second plurality offlaps, each flap comprising at least a first surface and beingpositionable between a first position and a second position wherein theflaps position between the first and second positions is determined independence upon the pressure applied by water impinging upon the firstsurface resulting from motion of the hull through the water.
 5. Thestructure according to claim 1 wherein, the first position of theplurality of flaps is substantially perpendicular to the hull; and thesecond position of the plurality of flaps is substantially parallel tothe hull.
 6. The structure according to claim 1 wherein; the firstposition of the plurality of flaps is such that they are inclined in amanner that a first end of the flaps closer to the hull surface isfurther from the bow of the water craft than a second end of the flapsthat are further from the hull surface.
 7. The structure according toclaim 1 wherein; the plurality of flaps are associated with at least twoflap groups of a plurality of flap groups, each flap group characterisedby a predetermined flap profile defining a position of the flap ss as afunction of water pressure.
 8. A device comprising: a nozzle mounted ina predetermined location on a hull of a water craft, the nozzlereceiving water from a channel forming a predetermined portion of thehull and exhausting said water to provide variable thrust for the watercraft between zero and a maximum thrust in dependence upon a controlsetting provided by a user of the water craft; a first flap comprisingat least a first plate and a first mounting, the first mounting forattaching the first plate to the hull in a predetermined locationrelative to the nozzle and being impinged upon by water during motion ofthe water craft and allowing the first plate to pivotably displacebetween a first predetermined position and a second predeterminedposition.
 9. The device according to claim 8 wherein, the predeterminedlocation of the first flap is such that a predetermined portion of thewater exiting the nozzle impinges upon the first flap; and the positionof the first flap varies between the first position and second positionin dependence upon at least the thrust provided by the nozzle.
 10. Thedevice according to claim 8 wherein, the predetermined location of thefirst flap is such that the water impinging on the first flap is notprimarily from the nozzle; and the position of the first flap variesbetween the first position and second position in dependence upon thevelocity of the water craft.
 11. The device according to claim 8 furthercomprising; a second flap comprising at least a second plate and asecond mounting, the second mounting for attaching the second plate tothe hull in a predetermined location relative to the nozzle and beingimpinged upon by water during motion of the water craft and allowing thesecond plate to pivotably displace between a third predeterminedposition and a fourth position.
 12. The device according to claim 11wherein, the first and second flaps are symmetrically disposed withrespect to at least one of an axis of the nozzle and an axis of thewater craft.
 13. The device according to claim 11 wherein, the first andsecond mountings are at least one of always in the nozzle exhaust anddisplaced laterally with respect to the nozzle exhaust.
 14. The deviceaccording to claim 8 wherein, the first plate comprises a base plate anda bladder, the bladder comprising a shell surrounding a chamber filledwith a predetermined gas at a predetermined pressure such that thebladder presents a variable profile to the water in dependence upon thepressure exerted by water flowing past the bladder as a result of atleast one of the nozzle water exhaust and motion of the water craft. 15.The device according to claim 14 wherein, the base plate comprises atleast a chamber of a plurality of chambers, each chamber linked to thebladder via a pressure valve such that gas movement between a chamberand the bladder was determined in dependence upon the pressure appliedto the bladder by water impinging upon the bladder.
 16. A devicecomprising: an engine comprising at least a drive shaft and operating independence upon an engine control signal; a first coupling selectablyengageable with a drive shaft of the engine and comprising a firstimpeller shaft; a first exhaust providing thrust to a water craftthrough the exhausting of water under pressure from the first exhaust,the pressure generated by a first impeller coupled to the first impellershaft; a second coupling selectably engageable with another drive shaftand comprising a second impeller shaft; a second exhaust providingthrust to a water craft through the exhausting of water under pressurefrom the second exhaust, the pressure generated by a second impellercoupled to the second impeller shaft, wherein the first and secondexhausts exhaust in opposite directions thereby allowing one of thefirst and second exhausts to provide driving thrust and the other of thefirst and second exhausts to provide braking thrust.
 17. The deviceaccording to claim 16 wherein; the selective engagement of the first andsecond couplings are each controlled in dependence upon at least thethrottle control signal.
 18. The device according to claim 16 furthercomprising: a third coupling selectably engageable with the anotherdrive shaft and comprising a third impeller shaft; a third exhaustproviding thrust to a water craft through the exhausting of water underpressure from the third exhaust, the pressure generated by a thirdimpeller coupled to the third impeller shaft; wherein the principle axisof thrust of the second and third exhausts are disposed at approximatelyequal but opposite angles with respect to the principle axis of thrustof the first exhaust thereby allowing each of the second and thirdexhausts to selectively provide at least one of braking thrust andsteering thrust to the water craft whilst the first exhaust selectivelyproviding driving thrust to the water craft.
 19. The device according toclaim 18 wherein, the first exhaust provides driving thrust independence upon at least a throttle control signal; and the second andthird exhausts provide at least one of braking thrust and steeringthrust in dependence upon at least the throttle control signal and asteering control signal generated in dependence upon an aspect of thesteering of the water craft.